Heat the oil in a large skillet over medium heat, and when it’s hot add the onion. Sauté for about 8 minutes until tender, but don’t let it get more than golden brown. Add the greens and sauté for another 4 or 5 minutes until they are wilted and tender.
While the greens are cooking, heat another skillet over medium heat. Add the sausages and cook, turning them somewhat frequently, for about 10 minutes until lightly browned and cooked through. Cut them into pieces that will comfortably fit into the buns.
Pile the greens and sausage in the buns. Eat.
Notes
There are a number of companies that make blends of greens called Power Blends or Power Greens, or something along those lines. They are usually a mix of sturdier greens like spinach, kale and chard, and while they might be a bit of a formidable presence in a salad, they are excellent sautéed up on their own or as part of a dish. These greens and onions also make a great side dish.